Thursday, January 07, 2016

Over the years we've looked at a number of attempts to use convalescent plasma - donated by survivors of H5N1, H1N1, H7N9, SARS and most recently MERS and Ebola - to treat infected patients.

Results have been mixed, but they’ve reported some success along the way.

Although in limited use today, human and animal serum therapy was
used extensively during the first half of the 20th century to treat a
variety of infectious diseases, including anthrax, scarlet fever,
measles, tularemia, diphtheria and rabies.

While often effective, a relatively high percentage of adverse reactions (serum sickness) along with the development of effective antibiotics and drugs, has seen its use decline.

But with a new crop of deadly infectious diseases - with few, if any therapeutic options - convalescent serum is getting a new life.

Over the past year there have been several small clinical trials using convalescent plasma conducted in Western Africa for treating Ebola and several Ebola patients in the United States received convalescent blood products as well.

While hopes have run high for this type of treatment, late yesterday the NEJM published the results of the first clinical trial of convalescent plasma therapy from the West African Ebola outbreak, and the results are disappointing:

Of 84 patients treated in this clinical trial, no statistically significant improvement in survival was noted over the control group.

There were limitations to this study, not the least of which was an inability to determine the level of antibodies in the donor plasma due to a lack of a BSL-4 lab in West Africa. It may well be that a serum containing a higher level of antibodies would produce a better result.

First a link to the NEJM report, then a link to Lisa Schnirring's excellent review on CIDRAP News.

A total of 84 patients who were treated with plasma were included in the primary analysis. At baseline, the convalescent-plasma group had slightly higher cycle-threshold values and a shorter duration of symptoms than did the control group, along with a higher frequency of eye redness and difficulty in swallowing. From day 3 to day 16 after diagnosis, the risk of death was 31% in the convalescent-plasma group and 38% in the control group (risk difference, −7 percentage points; 95% confidence interval [CI], −18 to 4). The difference was reduced after adjustment for age and cycle-threshold value (adjusted risk difference, −3 percentage points; 95% CI, −13 to 8). No serious adverse reactions associated with the use of convalescent plasma were observed.

In
a pair of new studies on Ebola treatment, a trial of convalescent
plasma at a treatment center in Guinea didn't find a significant
survival benefit, while patients at a Liberian treatment unit
unexpectedly seemed to benefit from a malaria drug combo clinicians gave
in response to a drug shortage.

Both studies were published today in the latest online edition of the New England Journal of Medicine (NEJM), alongside a shorter report on gender differences during the Ebola outbreak, such as higher survival rates in female patients.

While this particular trial did not produce the desired results, the idea of using convalescent serum to treat emerging infectious diseases like MERS, avian flu, and Ebola is far from dead. For some earlier blogs on the use of convalescent therapy, you may wish to revisit: